1. Field of the Invention
The present invention relates to a zoom lens system for use in cameras such as 35 mm single lens reflex cameras and so-called 110 size compact cameras, and more particularly to a zoom lens system having a front lens group, a variator lens group, a compensator lens group and a relay lens group.
In the above mentioned zoom lens system, the diameter of the system and the total length of the system relative to the focal length are generally increased in accordance with the increase of the field angle.
2. Description of the Prior Art
In this field, various forms of zoom lens systems have been suggested in the prior art such as disclosed in U.S. Pat. Nos. 3,584,935, 3,796,481, 3,840,290, 3,975,089 and Japanese Pat. Publication No. 51-26276.
The Japanese Patent Publication is of particular interest in that it discloses a type of varifocal lens system consisting of a front lens group of a positive refractive power, a variator lens group of a negative refractive power, and a compensator lens group of a negative refractive power, in which the variator lens group has three single lens elements. However, the image side surface of the second single lens element and the object side surface of the third single lens element in the variator lens group have almost the same radius of curvature. Further, the relay lens group of the Japanese Patent Publication consists of five separate lens elements, which are a first positive single lens element, a second positive single lens element, a considerably thick positive doublet element having a rear surface of a relatively short radius of curvature, a third positive single lens element and a negative single lens element from the object to the image side without any relatively wide air space formed between the separate elements.